Centrifugal separator



p 9, 1969 e. w. BRANDT CENTRIFUGAL SEPARATOH' 2 Sheets-Sheet 1 Filed Oct. 20. 1967 Fig. 1

p 9,1969 G. w. BRANDT 3,465,957

CEN'IRIFUGAL SEPARATOR Filed Oct. 20, 1967 2 Shuts-Sheet 2 \X 32. g y 36 1 United States Patent 3,465,957 CENTRIFUGAL SEPARATOR Gunnar Walter Brandt, Nykoping, Sweden, assignor t0 LKB-Produkter AB, Stockholm-Bromma, Sweden, :1 company of Sweden Filed Oct. 20, 1967, Ser. No. 676,777 Claims priority, application Sweden, Oct. 27, 1966, 14,728/ 66 Int. Cl. B04b 9/12; B01d 21/26 U.S. Cl. 23326 9 Claims ABSTRACT OF THE DISCLOSURE The invention is concerned with a centrifugal separator for the batchwise treatment of a liquid. The invention is preferably concerned with the treatment of a comparatively small volume of liquid, for instance for the separation in an analysis laboratory of a heavier phase of a solution or mixture from a lighter one. An interesting field of use for the invention is the treatment of blood, for the separation of blood serum or blood plasma from the other constituents of the blood.

A conventional type of centrifugal separators is the so-called bottle centrifuges, in which the sample to be treated is applied in bottles or tubular containers, and a plurality of such bottles or containers are placed in a rotor which is then rotated at a high speed. The heavier particles or phase collects on the bottom of the containers. In order to balance the rotor it is necessary to determine the quantity of the samples carefully, or to apply counterweights at diametrically opposite bottles or containers.

If the sample consists of blood which has been transferred from the blood donor into tubes which cannot be directly placed into the centrifugal separator the blood has to be transferred from said tubes into tubes designed for the separator. In said transfer of the blood from one tube to another coagulated particles have to be loosened from the wall of the first tube, which has to be done carefully as hemolysis may otherwise result, that is an undesired destruction of the blood corpuscles. This operation is not only complicated but also requires a lot of time and a high cost.

The invention is concerned with another type of centrifugal separators, the so-called tube centrifuges. This type of centrifuges is characterized in that the centrifuge container is brought to rotate around its longitudinal axis, resulting in that the heavier phase of the sample collects at the wall of the container whereas the lighter phase collects more remote from the wall, that is nearer the central axis of the container. A system of knives or baflle plates or similar means may be used for separating the two phases from each other. If a centrifugal separator of this "'ice type is to be used for analytical operations it is necessary to check, before a new sample is added, that the apparatus has been cleaned so that residues from the previous sample do not contaminate the new sample.

It is an object of the invention to provide a centrifugal separator of the tube centrifuge type, permitting manual operations to be avoided as far as possible in the handling of the sample and in the charging of the centrifugal separator. It is another object of the invention to provide a centrifugal separator which can be operated without any danger of one sample contaminating another sample. It it another object of the invention to provide a centrifugal separator in which the separated phases of the sample do not again mix with each other during the continued treatment in the apparatus.

The centrifugal separator according to the invention is characterized in comprising a centrifugal body arranged to be rotated at a high speed, a tubular container for the liquid, said container being arranged centrally and axially in the centrifugal body, a receptacle which is releasably fastened to the open end of the container and which has a larger diameter than the container, and a narrow portion at the open end of the tubular container, said narrow portion retaining the heavier phase in the container while allowing the lighter phase to flow out into the receptacle.

The invention will now be explained with reference to the accompanying drawings which illustrate two embodiments which are designed for treating blood samples in order to separate blood serum or blood plasma from the other constituents of the blood. FIG. 1 represents an axial cross sectional view of a first embodiment, FIG. 2 shows the apparatus of FIG. 1 as seen from above, and FIG. 3 illustrates a second embodiment.

The apparatus illustarted in FIGS. 1 and 2 contains a tube 1 having one closed end. The upper end of the tube supports a receptacle 3 containing an annular chamber 19 and having an opening 4 in the conical upper wall. The receptacle has a central hub 18 which is releasably fastened to the tube 1 by means of conical surfaces 6. These surfaces 6 constitute a tight joint, preventing liquid from leaking out between the tube 1 and the receptacle 3. The conical portion 6 of the tube forms a shoulder 2 which engages a corresponding shoulder on the lower portion of the hub. The upper portion of the hub has a flange 5 which is directed inwardly, thus acting as a narrow portion which is so dimensioned that there is a sufiicient annular space between the inner surface of 7 said narrow portion and the inner surface of the tube to contain the heavier phase of the sample. The lighter phase will be brought into a position nearer the axis of rotation, and will consequently flow over the narrow portion, thus being collected in the annular chamber 19.

In operation a blood sample is transferred from the blood donor to .a tube 1. The tube is now inserted into the hub of a receptacle, so that the shoulder 1 comes into resilient engagement with the shoulder of the hub. The tube-receptacle assembly is now inserted into a centrifugal body 7 having a first bore to fit the tube 1 and a second bore of a larger diameter to fit the receptacle 3. The centrifugal body 7 is now closed by means of a lid 9. The lid has three spring operated locking members 11 pivoted on screws 16 and connected to each other by means of springs 17. The rotation forces the locking members outwardly to engage into a groove 13 in the centrifugal body 3 7, thus fastening the lid 9. The centrifugal body 7 is mounted on a shaft 15 which is rotated by a motor. The means for rotating the centrifugal body 6 do not form part of the invention, and will not be described here.

The two phases of the blood sample shall be given sufficient time to separate from each other. Therefore, the speed of the centrifugal body shall first be limited so that the sample does not fiow over the narrow portion before the phases have separated. The blood forms a layer 20 on the wall of the tube 1. Now the speed is increased so much that the lighter phase, that is the blood serum or plasma, flows over the narrow portion 5 into the annular chamber 19, while the heavier phase, mainly consisting of blood corpuscles, is retained in the tube 1 by the flange 5. The centrifuge is now stopped, resulting in the locking members 11 being moved towards the centre by the springs 17.

The tube-receptacle assembly is now lifted out of the tube 1, preferably by means of a tool which is inserted into the opening 4. The tube 1 is now pulled apart from the receptacle. The lighter phase can now be poured from the receptacle through the opening 4. The centrifugal body 7 is now ready to receive another tube-receptacle assembly. The apparatus need not to be cleaned, since there has not been any contamination of the centrifugal body 7 or the lid 9.

The inner diameter of the narrow portion 5 and its relation to the inner diameter of the tube 1 is chosen dependent on the volume of the sample and on the percentage of the sample desired to form the lighter phase. In the illustrated embodiment the narrow portion which retains the heavier phase in the tube 1 is formed by the flange 5. It is within the scope of the invention to arrange said narrow portion on the interior wall of the tube 1, for instance as a thickened portion of the tube wall.

The tube 1 and the receptacle 3 should preferably consist of plastics. When being centrifuged the tube and the receptacle expand to come into close engagement with the walls of the bores of the centrifugal body. After having been centrifuged the tube and the receptacle contract again, due to the elasticity of the plastics, so that they can be removed from the centrifugal body. The tubereceptacle assembly made of plastics is inexpensive and can be disposed of after one use.

FIG. 3 illustrates an apparatus in which the tubereceptacle assembly is inserted into the centrifuge rotor from below. The apparatus is particularly designed as a high capacity apparatus to centrifuge a large number of blood samples per unit of time, the tube-receptacle units being automatically inserted into and withdrawn from the apparatus. However, the transport means for supplying and withdrawing the tube-receptacle units do not form part of this invention, and are not to be described here.

The tube-receptacle unit illustrated in FIG. 3 is mainly of the same type as that of FIGS. 1 and 2, and the same reference characters have been used. The apparatus contains a stationary support 31. The support contains a rotor, consisting of .a lower tubular portion 32 and an upper tubular portion 33 of a lesser diameter. The rotor is rotatably fastened to the support by means of a ball bearing at 35. A belt pulley 34 is fastened to the upper tubular portion 33, to rotate the rotor from a motor, not shown, over an endless belt.

The lower tubular portion 32 has a first zone 36 having a diameter allowing the tube-receptacle unit 1, 3 to be readily inserted through the lower open ends of the support 31 and the rotor 32, and a second zone 37, separated from the first zone 36 by a shoulder 3, having a somewhat reduced diameter fitting exactly the diameter of the receptacle 3.

The lower open end of the rotor 32 carries a plurality of spring-actuated arms 41, 42 which are pivoted on pins 43. When the rotor is stationary the arms take the position indicated in full lines. When the rotor is rotating the centrifugal force acts upon the heavier portion 41 to move the arms, against the action of the springs, into the position indicated in dotted lines. A rounded surface 44 engages the bottom of the tube 1, to hold the tube steady during the operation.

The centrifugal operation having been finished a rod 39 in the upper portion 33 of the rotor is pressed down. The lower end of the rod 39 carries a plunger-like member 40 which moves the receptacle 3 down and out of engagement with the zone 37 of the rotor 32.

EXAMPLE In the apparatus of the kind illustrated in FIGS. 1 and 2 the tube 1 had a length of mm. and an inner diameter of 10.3 mm. The opening defined by the portion 5 had a diameter of 9.6 mm. The tube was charged with 5 ml. of blood, and was first centrifuged at 3500 r./min. for 20-30 seconds, which was sufficient for separating the blood plasma from the other constituents of the blood. The speed was now increased to 6000 r./min. for a few seconds, resulting in 2.5 ml. of blood plasma flowing over the narrow portion 5 into the receptacle.

What is claimed is:

1. A centrifugal separator for the batchwise treatment of a liquid, preferably a comparatively small volume of liquid, characterized in comprising a centrifugal body (7) arranged to be rotated at a high speed, a tubular container (1) for the liquid, said container being arranged centrally and axially in the centrifugal body, a receptacle which is releasably fastened to the open end of the container and which has a larger diameter than the container, and a narrow portion (5) at the open end of the tubular container (1), said narrow portion retaining the heavier phase in the container (1) while allowing the lighter phase to flow out into the receptacle (3).

2. A centrifugal separator as claimed in claim 1, characterized in that the narrow portion consists of an inwardly directed flange (5) 0n the receptacle.

3. A centrifugal separator as claimed in claim 1, characterized in that the receptacle (3) has a central hub (18) which can be releasably fastened to the open end of the container (1), and an annular chamber (19) around the hub for collecting the lighter phase.

4. A centrifugal separator as claimed in claim 3, characterized in that the receptacle (3) has an opening (4) in its upper portion, making it possible to pour the collected lighter phase from the receptacle.

5. A centrifugal separator, comprising a centrifuge body, means for rotating said centrifuge body, a first bore in the centrifuge body, coaxial with the axis of rotation, a second bore in the centrifuge body, coaxial with the axis of rotation and having a larger diameter than the first bore, in said first bore a tube having a bottom and an open upper end and having a diameter to fit the bore, in said second bore a receptacle having an outer wall to fit the bore and a central hub to fit the upper, open end of the tube, said outer wall and said central hub defining between them an annular chamber, said hub having a flange-like upper portion defining an opening having a diameter less than that of the tube.

6. A centrifugal separator as claimed in claim 5, in which the receptacle has a conical upper wall with a central opening, a lid being detachably fastened to the centrifuge body to engage said conical upper wall of the receptacle.

7. A centrifugal separator as claimed in claim 6, in which the lid has spring-actuated locking members arranged to move outwardly into locking engagement with the centrifuge body by the centrifugal force, against the action of the springs.

8. A centrifugal separator, comprising a tubular rotor having an open lower end, means for rotating said tubular rotor around its axis, in said tubular rotor a tube having a bottom and an open upper end, in said tubular rotor a receptacle having an outer wall to fit the inner wall of the References Cited rotor and a central hub to fit the upper open end of the P NT tube, said hub having a flange-like upper portion de- UNITED STATES ATE S fining an opening having a diameter less than that of the 1,277,653 9/1918 sharples 233*27 tube, and pivoted arms on the rotor to be actuated by 5 3,115,460 12/1963 MFcormlck 233 26 the centrifugal force to support the lower end of the tube 3,133832 5/1964 Mltchen et 23 326 durin operation.

9. Z centrifugal separator as claimed in claim 8, com- WILLIAM PRICE Primary Exammer prising means in the upper end of the rotor to push the US. Cl. X.R. receptacle down and out of engagement with the rotor. 10 2331 

